Effect Of Different Nitrogen Forms On Upland Rice Yield And Its Cause Analysis

China is a big country of rice production and consumption.The main characteristics of rice planting are high input of water and fertilizer,low utilization rate,and negative impact on the environment.No flood irrigation is needed during the whole growth period of upland rice,which can save 70%of water compared with rice.It has the characteristics of drought tolerance,barren tolerance and wide adaptability.Rice prefers ammonium nitrogen,but it is controversial as to which form of nitrogen the upland rice prefers to absorb.The experiment was carried out at the experimental farm of Yangzhou University from 2017 to 2018.Indica upland rice Baohan 1 and Japonica upland rice Zhenghan 10 were selected as the test materials.Five different levels of ammonium and nitrate were set,namely NH4+-N Ammonium sulfate)and NO3--N(sodium nitrate)(100%/0(C1),75%/25%(C2),50%/50%(C3),25%/75%(C4),0%/100%(C5),to study the effects of combination ratio on photosynthetic characteristics,morphological and physiological characteristics,nitrogen nutrition characteristics,yield and composition of upland rice and their relationship.The main results are as follows:Both Baohan 1 and Zhenghan 10 were C3 treated,that is,under the condition of 1:1 mixture of ammonium nitrogen and nitrate nitrogen,their SPAD value,net photosynthetic rate,dry matter weight,number of spikes,spikes The rate,economic coefficient and output are the largest and highest.Correlation analysis showed that dry matter weight and SPAD value were significantly or extremely significantly positively correlated with thousand-grain weight and yield(r=0.896*～0.981**).With the decrease of the ratio of ammonium nitrogen to nitrate nitrogen,the root length,root volume,root surface area,indefinite number of roots and the percentage of root active absorption area show a trend of increasing first and then decreasing;root diameter,active absorption area,The total absorption area,specific surface area,root injury flow rate,amino acid content,NR activity,GS and GDH showed a gradual decrease trend,and the root characteristics were generally the best when treated with C3.Correlation analysis showed that root weight,root length,and root volume were significantly or extremely significantly positively correlated with yield(r=0.880*～0.968**),and root weight,root volume,and indefinite root number were significantly or very significantly positively correlated with thousand-grain weight(r=0.889*～0.987**).At jointing stage,heading stage and maturity stage,the nitrogen content of rice plant increased first and then decreased with the decrease of the ratio of ammonium nitrogen to nitrate nitrogen.The nitrogen content of rice plant under C3 treatment was higher than that of other treatments,and that of C5 treatment was the lowest.The content of nitrate nitrogen in leaves,soil pH and soil increased with the decrease of the ratio of ammonium to nitrate,but the content of ammonium nitrogen in soil was the opposite.The correlation analysis showed that the nitrogen content of upland rice had significant or extremely significant positive correlation with 1000 grain weight(r=0.900*,0.997**);the specific surface area and amino acid content had significant positive correlation with soil ammonium nitrogen(r=0.889*～0.939*);the specific surface area and amino acid content had significant negative correlation with soil nitrate nitrogen(r=-0.891*～0.993**);the active absorption area and total absorption area There was a significant negative correlation(r=-0.896*～-0.938*)between them.Under the 1:1(C3)treatment of ammonium nitrogen and nitrate nitrogen,upland rice has strong tillering ability,developed root system,high ear formation rate,strong photosynthetic ability,large dry matter weight and nitrogen accumulation,number of spikes,seed setting rate,thousand kernel weight The largest,this is an important reason why its output is higher than other treatments.It is suggested that the fertilization method with 1:1 ratio of ammonium nitrogen and nitrate nitrogen in upland rice practice is beneficial for upland rice to save water and increase production.